STUDIES IN THE CHEMICAL CONSTITUENTS OF ERIGERON CANADENSIS (CONYZA CANADENSIS) AND BERCHEMIA PAKISTANICA

Abstract

The art of healing has its origin in the antiquity of human civilization. Even in prehistoric times, the man was fully able to distinguish those plants, which had healing properties from those having toxicities. Great reservoirs of knowledge on medicinal plants have been provided by Chinese, Sumerian, Babilonian, Egyptian, Greek and Muslim civilizations. In the Indo-Pakistan subcontinent records of the indigenous system of medicine known as Ayurveda, go back to 700 B.C. and its systematization is attributed to Charaka and Susruta, who have cited about seven hundred medicinal plants. In Indo-Pakistan subcontinent, there has been a fairly organized effort for pharmacological studies in the physiologically active plant constituents. Various centers have been established in both India and Pakistan for systematic studies on medicinal plants. The most recent and sophisticated amongst these is H.E.J. Research Institute of Chemistry, University of Karachi, where bioassay directed isolation studies of active plant constituents are routinely carried out. These studies have already resulted in hundreds of new natural products possessing promising potentials for the treatment of serious human ailments like aids, tumor, diabetes, hypertension, etc.
The present thesis describes the bioassay directed isolation studies of bioactive natural products from two medicinal plants namely Erigeron Canadensis (syn. Conyza Canadensis) and Berchemia Pakistanica. Both of these occur in southern parts of Pakistan and are used by local physicians for the treatment of a variety of ailments. The thesis, is therefore, presented in two parts namely: Part-A Studies in the Chemical Constituents of Erigeron Canadensis (Syn. Conyza Canadensis Linn). Part-B Studies in the Chemical Constituents of Berchemia Pakistanica Browicz ÃÂÃÂ¢ÃÂÃÂÃÂÃÂStudies in the Chemical Constituents of Erigeron Canadensis (Syn. Conyza Canadensis Linn.)ÃÂÃÂ¢ÃÂÃÂÃÂÃÂ
Phytochemical studies on the methanolic extract of the whole plant material have resulted in the isolation and structural elucidation of five new sphingolipids along with nine other compounds reported for the first time from this species.
Known Compounds from Erigeron Canadensis ÃÂÃÂÃÂÃÂ²-Sitosterol 171 Stigmasterol 172 ÃÂÃÂÃÂÃÂ²-Sitosterol 3-O- ÃÂÃÂÃÂÃÂ²-D-glucopyranoside 173 Harmine 174 p-Hydroxybenzoic acid 175 3,5-Dihydroxybenzoic acid 176 3,5-Dimethoxybenzoic acid 177 3 ÃÂÃÂÃÂÃÂ²-Hydroxyolean-12-en-28-oic acid 178 3 ÃÂÃÂÃÂÃÂ²-Erythrodiol 1879
ÃÂÃÂ¢ÃÂÃÂÃÂÃÂStudies in the Chemical Constituents of Berchemia Pakistanica BrowiczÃÂÃÂ¢ÃÂÃÂÃÂÃÂ Phytochemical studies on the methanolic extract of the whole plant material have resulted in the isolation and structural elucidation of four new compounds along with nine other compounds reported for the first time from this species.
Known Compounds from Berchemia Pakistanica 7.5ÃÂÃÂ¢ÃÂÃÂÃÂÃÂ-Dimethoxy-3,5,2ÃÂÃÂ¢ÃÂÃÂÃÂÃÂ-trihydroxyflavone 235 4ÃÂÃÂ¢ÃÂÃÂÃÂÃÂ,5-Dihydroxy-3,6,7-trimethoxyflavone 236 5,6-Dihydroxy-4,7-dimethoxy-2-methylanthracene-9,10-dione 237 1,3,4-Trihydroxy-6,7,8-trimethoxy-2-methylanthracene-9,10-dione 238 ÃÂÃÂÃÂÃÂ²-Sitosterol 239 ÃÂÃÂÃÂÃÂ²-Sitosterol 3-O- ÃÂÃÂÃÂÃÂ²-D-glucopyranoside 240 Vavain 241 Daphnin 242 Daphnetin 8-O- ÃÂÃÂÃÂÃÂ²-D-glucopyranoside 243
Pharmacological screening of sphingolipids 166-170 revealed significant tyrosinase inhibiting activity of 167,moderate tyrosinase inhibiting activity in 166,169 and 170,while 168 was inactive. Pakistolides A 231 and B 232 showed significant inhibitory activities against lipoxygenase and a-glucosidase enzyme. In addition, Pakistolide B 232 also revealed strong antioxidant activity. Berchemins A 233 and B 234 showed strong glipoxygenase inhibiting activity. The latter also showed strong inhibition against a-glucosidase while former was moderately active.
From these findings it is obvious that all of the newly isolated compounds except 168 have potentials to be used in the treatment of skin diseases, human-immunodeficiency virus (HIV), tumor, bronchial asthma and inflammation.